226 research outputs found
Modified gravity inside astrophysical bodies
Many theories of modified gravity, including the well studied Horndeski
models, are characterized by a screening mechanism that ensures that standard
gravity is recovered near astrophysical bodies. In a recently introduced class
of gravitational theories that goes beyond Horndeski, it has been found that
new derivative interactions lead to a partial breaking of the Vainshtein
screening mechanism inside any gravitational source, although not outside. We
study the impact of this new type of deviation from standard gravity on the
density profile of a spherically symmetric matter distribution, in the
nonrelativistic limit. For simplicity, we consider a polytropic equation of
state and derive the modifications to the standard Lane-Emden equations. We
also show the existence of a universal upper bound on the amplitude of this
type of modified gravity, independently of the details of the equation of
state.Comment: 11 pages, 6 figure
Sirt1 expression is associated with CD31 expression in blood cells from patients with chronic obstructive pulmonary disease
Background: Cigarette smoke induced oxidative stress has been shown to reduce silent information regulator 1 (Sirt1) levels in lung tissue from smokers and patients with COPD patients. Sirt1 is known to inhibit endothelial senescence and may play a protective role in vascular cells. Endothelial progenitor cells (EPCs) are mobilized into circulation under various pathophysiological conditions, and are thought to play an important role in tissue repair in chronic obstructive lung disease (COPD). Therefore, Sirt1 and EPC-associated mRNAs were measured in blood samples from patients with COPD and from cultured CD34+ progenitor cells to examine whether these genes are associated with COPD development. Methods: This study included 358 patients with a smoking history of more than 10 pack-years. RNA was extracted from blood samples and from CD34+ progenitor cells treated with cigarette smoke extract (CSE), followed by assessment of CD31, CD34, Sirt1 mRNA, miR-34a, and miR-126-3p expression by real-time RT-PCR. Results: The expression of CD31, CD34, Sirt1 mRNAs, and miR-126-3p decreased and that of miR-34a increased in moderate COPD compared with that in control smokers. However, no significant differences in these genes were observed in blood cells from patients with severe COPD compared with those in control smokers. CSE significantly decreased Sirt1 and increased miR-34a expression in cultured progenitor cells. Conclusion: Sirt1 expression in blood cells from patients with COPD could be a biomarker for disease stability in patients with moderate COPD. MiR-34a may participate in apoptosis and/or senescence of EPCs in smokers. Decreased expression of CD31, CD34, and miR-126-3p potentially represents decreased numbers of EPCs in blood cell from patients with COPD
Scan-less full-field fluorescence-lifetime dual-comb microscopy using two-dimensional spectral mapping and frequency multiplexing of dual-optical-comb beats
Fluorescence lifetime imaging microscopy (FLIM) is a powerful tool for
quantitative fluorescence imaging because fluorescence lifetime is independent
of concentration of fluorescent molecules or excitation/detection efficiency
and is robust to photobleaching. However, since FLIM is based on point-to-point
measurements, mechanical scanning of a focal spot is needed for forming an
image, which hampers rapid imaging. In this article, we demonstrate scan-less
full-field FLIM based on a one-to-one correspondence between two-dimensional
(2D) image pixels and frequency-multiplexed RF signals. A vast number of
dual-optical-comb beats between dual optical frequency combs is effectively
adopted for 2D spectral mapping and high-density frequency multiplexing in
radio-frequency region. Bimodal images of fluorescence amplitude and lifetime
are obtained with high quantitativeness from amplitude and phase spectra of
fluorescence RF comb modes without the need for mechanical scanning. The
proposed method will be useful for rapid quantitative fluorescence imaging in
life science.Comment: 38 pages, 8 figures, 1 tabl
Multicascade-linked synthetic wavelength digital holography using an optical-comb-referenced frequency synthesizer
Digital holography (DH) is a promising method for non-contact surface
topography because the reconstructed phase image can visualize the nanometer
unevenness in a sample. However, the axial range of this method is limited to
the range of the optical wavelength due to the phase wrapping ambiguity.
Although the use of two different wavelengths of light and the resulting
synthetic wavelength, i.e., synthetic wavelength DH, can expand the axial range
up to a few tens of microns, this method is still insufficient for practical
applications. In this article, a tunable external cavity laser diode
phase-locked to an optical frequency comb, namely, an optical-comb-referenced
frequency synthesizer, is effectively used for multiple synthetic wavelengths
within the range of 32 um to 1.20 m. A multiple cascade link of the phase
images among an optical wavelength (= 1.520 um) and 5 different synthetic
wavelengths (= 32.39 um, 99.98 um, 400.0 um, 1003 um, and 4021 um) enables the
shape measurement of a reflective millimeter-sized stepped surface with the
axial resolution of 34 nm. The axial dynamic range, defined as the ratio of the
maximum axial range (= 0.60 m) to the axial resolution (= 34 nm), achieves
1.7*10^8, which is much larger than that of previous synthetic wavelength DH.
Such a wide axial dynamic range capability will further expand the application
field of DH for large objects with meter dimensions.Comment: 19 pages, 7 figure
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